1. Field of the Invention
The present invention relates to a method of estimating sound arrival direction capable of accurately estimating the arrival direction of sound input from a sound source using multiple microphones even if ambient noise is present. The present invention further relates to a sound arrival direction estimating apparatus for carrying out the above-mentioned method, and a computer program product for achieving the above-mentioned apparatus using a general purpose computer.
2. Description of Related Art
Thanks to the progress of computer technology in recent years, even sound signal processing requiring a large amount of operation processing has become able to be carried out at a practical processing speed. Under these circumstances, a multi-channel sound processing function that uses multiple microphones is expected to come into practical use. A sound arrival direction estimating process for estimating the arrival direction of a sound signal is used as an example thereof. The sound arrival direction estimating process is a process for obtaining the delay time when a sound signal from a target sound source arrives at two of multiple microphones installed apart from each other with an interval and for estimating the arrival direction of the sound signal from the sound source on the basis of the difference between the arrival distances from the microphones and the installation interval between the microphones.
In a conventional sound arrival direction estimating process, for example, the correlation between signals inputted from two microphones is calculated, and the delay time between the two signals, at which the correlation becomes maximum, is calculated. Because the difference between the arrival distances is obtained by multiplying the calculated delay time by the transmission speed of sound in the air at the normal temperature, 340 m/s (changing according to the temperature), the arrival direction of the sound signal is calculated from the installation interval of the microphones using trigonometry.
Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 2003-337164, it is possible that the phase difference spectrum for each of the frequencies of the sound signals inputted from two microphones is calculated, and the arrival direction of the sound signal from a sound source is calculated on the basis of the inclination of the phase difference spectrum in the case that linear-approximation is carried out on frequency domain.